Project 3 will test the efficacy of a mass media campaign to help adolescent cigarette smokers stop smoking. Although it is well documented that smoking in adolescence is a serious problem, there is very little evidence of effective strategies to help teens quit smoking. Mass media hops the potential to reach large numbers of adolescent smokers, to influence the youth culture that supports smoking, and to demonstrate ways to help teens quit smoking through the depiction of smoking resistance behaviors performed by credible peers in appealing lifestyle contexts. This smoking cessation study will identify a cohort of 2400 youth who are at least weekly cigarette smokers in Grades 7, 8, 9, and 10 drawn form four intervention and four control media markers in four states, and assess these youth through annual telephone surveys for three consecutive years. Adolescents in the intervention areas will be exposed to targeted media messages based on principles derived from social cognitive theory and developed through diagnostic and formative research with youth from the targeted population. The media development process will be implemented in conjunction with Project 1 of this Program Project; message dissemination will occur in collaboration with the Communication Core. The annual telephone interviews will assess the impact of the three-year mass media campaign on smoking behavior outcomes, and on mediating variables including self-efficacy, outcome expectations, and perceptions of peer norms. Exposure to the media messages and other smoking- related influences within the media markets will be monitored, and a cost- effectiveness analysis will be performed. This study represents the first test of a large-scale mass media campaign focused entirely on adolescent smoking cessation using a message development process that was effective in prior adolescent smoking prevention research.